Calculator



FIG. 1 is a front elevation view of a calculator showing my new design;

FIG. 2 is a left side elevation view thereof;

FIG. 3 is a back elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof.

The broken lines depict environmental subject matter only and form no part of the claimed design. 

What is claimed is the ornamental design for a calculator, as shown and described. 